| Terry Schwartz <tschw10117@aol.com>: Jan 24 08:59AM -0800 Yes -- I imagine that is true, hence the need for finer control at lower volume levels. Terry |
| Terry Schwartz <tschw10117@aol.com>: Jan 24 09:03AM -0800 On Wednesday, January 24, 2018 at 10:59:48 AM UTC-6, Terry Schwartz wrote: > Yes -- I imagine that is true, hence the need for finer control at lower volume levels. > Terry Actually, I think the ear responds in an anti-log fashion. Small changes in audio source output levels are perceived as large changes at lower volume levels. Not so much at higher levels, where the ear essentially "saturates" and cant tell the difference between 90dB and 100dB (numbers pulled out of nowhere as examples) So the log curve on the pot compensates for this. |
| tabbypurr@gmail.com: Jan 24 10:51AM -0800 On Wednesday, 24 January 2018 17:03:50 UTC, Terry Schwartz wrote: > > Yes -- I imagine that is true, hence the need for finer control at lower volume levels. > > Terry > Actually, I think the ear responds in an anti-log fashion. Small changes in audio source output levels are perceived as large changes at lower volume levels. Not so much at higher levels, where the ear essentially "saturates" and cant tell the difference between 90dB and 100dB (numbers pulled out of nowhere as examples) So the log curve on the pot compensates for this. AIUI log pots were never really log. They normally used 2 resistance zones to give a very crude approximtion of a log law. It was good enough for audio, where the aim was to avoid everything happening down the bottom end of travel. NT |
| "Gareth Magennis" <soundserviceleeds@outlook.com>: Jan 24 09:23PM wrote in message news:aa7420bf-47db-4c33-a3f6-2bfd9cb05d88@googlegroups.com... >"I had a go at rewinding a wire-wound log pot one time, it survived a year and then something went wrong. " I repaired a variac a while back. Obviously it was linear. Luckily I caught it in time as it was rubbing the wiper over a winding that was popped out of place and it would have broken soon. But don't confuse a variac with a pot, a variac actually works like a transformer. Now if one were to feed it DC it would be nothing but a pot, and likely burn up unless you kept the input voltage down. But a little bit of glue took care of it, good thing too as it was one of the ones that go up to 150 VAC. ************************************* Pah, mine goes to over 260 VAC. Gareth. |
| oldschool@tubes.com: Jan 24 03:23PM -0600 On Wed, 24 Jan 2018 06:02:37 -0800 (PST), "pfjw@aol.com" <pfjw@aol.com> wrote: >but nothing on pots, linear or rotary. >Peter Wieck >Melrose Park, PA That's exactly what I found on the web. In other words, NOTHING regarding the K-taper. But I did find the W-taper and it was explained the same as you said. I found some forum where they were discussing pot tapers and some mentioned even more letters, such as N, S, M, D, and a few more. But not K. And yea, I managed to bring up drill bits too. That forum is here: http://www.diystompboxes.com/smfforum/index.php?topic=92918.0 This pot is R60, (master volume control). It's a unusual type of pot in the sense it's mounted to the PCB and mounted backwards, meaning there is a small piece of metal (ring) attached to it's rear, that is soldered to the PCB and the three tabs are bent downward, where they are soldered to the PCB. I have not yet taken it off the board. The pot does work, but the shaft is broken below the front panel surface. My first thought is to contact Altec Lansing and see if I can get an exact replacement. If not, I may try to saw off the remaining plastic shaft so it's flat, and make up a "sleeve" for it, (a piece of metal tubing) and glue another shaft to it with the tubing to reinforce it. This shaft should be about 1.5 inch long, (before being broken) so I have room to work, since there is still a half inch to work with. If none of that works, I'll have to Mcgyver some other pot in there, and will choose an audio taper type. With any luck, Altec will have a replacment part. That would be the easiest fix. A while back, I found out that Peavey electronics does have parts for all their old stuff. I hope Altec Lansing does too. For reference, there is a lot of useful info about pots on this website. http://www.potentiometers.com/potcomFAQ.cfm?FAQID=29 |
| "pfjw@aol.com" <pfjw@aol.com>: Jan 24 01:34PM -0800 > I have not yet taken it off the board. The pot does work, but the shaft > is broken below the front panel surface. JB Weld is your best friend. Get a soda-straw or heat-shrink tubing about the same diameter as the shaft, either use the broken piece or a suitable bit of solid material to extend the shaft to the correct length. Mix up the *SLOW* JB Weld epoxy, and use the straw/tubing to hold the shebang together and vertical, but out of the pot, until the epoxy sets up. Let the epoxy fill any voids. The result will be stronger than the original. Peter Wieck Melrose Park, PA |
| oldschool@tubes.com: Jan 24 03:39PM -0600 On Wed, 24 Jan 2018 05:48:52 -0800 (PST), Terry Schwartz >back of the pot, without sacrificing low level volume control. The switch often > requires a 15 or 20 degree rotation in order to activate -- using up part of the > pot travel. This is something I never even thought about, but it makes a lot of sense. I recall buying replacment pots for old tube gear, some 45 or more years ago, and you bought them without a switch, and bought the switch separately, which then attached to the rear of the pot. Apparently those pots were made to be used with a switch, but also worked without one. I never noticed any "dead spots" on them, or had problems where I could not turn the volume down low enough. Apparently that was all taken into consideration when they were made. But back then, it was a lot simpler. You chose audio and linear taper, and the correct resistance, and shaft length. That was about it. I recall getting many with LONG shafts that had to be sawed off and a flat spot filed onto the shaft. The good thing back then is that the shafts were all metal and did not break off. |
| bruce2bowser@gmail.com: Jan 24 02:03PM -0800 > > You probably have, in instrumentation somewhere. Just not marked as such. Like the intensity control of a scope or some shit like that. I could see there being applications like that. And some things just give you a part number and that's it. > > I do bet they're rare though. > What you been smokin? Have you ever dipped the tip of a cigarette in gasoline and tried it? |
| Phil Allison <pallison49@gmail.com>: Jan 24 02:34PM -0800 Terry Schwartz wrote: ------------------------ > Actually, I think the ear responds in an anti-log fashion. Small changes > in audio source output levels are perceived as large changes at lower > volume levels. ** Like other senses, hearing responds to *percentage" changes in sound level. The ideal volume control produces similar percentage changes for similar rotations or small movements. Good "log" pots have three linear sections that approximate the ideal fairly well. .... Phil |
| jurb6006@gmail.com: Jan 24 03:15PM -0800 >"Pah, mine goes to over 260 VAC. " Don't try to pull that cotton/polyesther wool substitute over my eyes. Your nominal line voltage is 240. So that means it is like me having one that goes to 130. Yours would have to go to 150 to be equivalent. What impresses me (some) is how some of these modern power supplies can handle auto-swicthing between line voltages. |
| MOP CAP <email@domain.com>: Jan 24 04:28PM -0800 As soon as my son teaches me how to scan on my new printer, I will post an old catalog page with many tapers shown. I will try to put in the drop box. I think the page was from an old Centralab catalog. CP |
| KenO <kenitholson@yahoo.com>: Jan 24 09:18AM -0800 Hi, A while ago put a number of HDDs in storage. Recently tried to use and noticed that some do Not spin up (all were working when put in storage). Had read that sometimes the heads will stick or other factors like lube will cause the disk from spinning. Did some searching and found https://groups.google.com/forum/#!searchin/sci.electronics.repair/how$20test$20no$20spin$20hard$20drives%7Csort:date/sci.electronics.repair/WH68qfkAAfM/51WIPwZL8yMJ https://groups.google.com/forum/#!searchin/sci.electronics.repair/how$20test$20no$20spin$20hard$20drives%7Csort:date/sci.electronics.repair/CDnXwrweST0/6_Sr72pRKUsJ for specific HDDs but to date No general info on what to test. Googled using how test "Hard drives" got a lot of hits but nothing helpful to no spin testing to date. Then decided to try http://www.repairfaq.org and searched with how test "Hard drives" but only got "The Drexel mirror site of the Sci.Electronics.Repair FAQ is temporarily unavailable..." Appreciate any suggestions Ken |
| Sjouke Burry <burrynulnulfour@ppllaanneett.nnll>: Jan 24 07:09PM +0100 On 24-1-2018 18:18, KenO wrote: > Then decided to try http://www.repairfaq.org and searched with how test "Hard drives" but only got "The Drexel mirror site of the Sci.Electronics.Repair FAQ is temporarily unavailable..." > Appreciate any suggestions > Ken I have "repaired"an old DOS computer with a stuck harddisk. Just gave the case a hard jerk around. It worked. Then made a backup............(it was not MY computer). So give the HD a gentle slam to rotate it and see if it works. If not slam some more. The disk might wake up. Do this in off state, then test. |
| "pfjw@aol.com" <pfjw@aol.com>: Jan 24 10:30AM -0800 Or as my old carpenter foreman used to say: When in doubt, get a bigger hammer! Peter Wieck Melrose Park, PA |
| tabbypurr@gmail.com: Jan 24 10:54AM -0800 On Wednesday, 24 January 2018 17:18:36 UTC, KenO wrote: > Then decided to try http://www.repairfaq.org and searched with how test "Hard drives" but only got "The Drexel mirror site of the Sci.Electronics.Repair FAQ is temporarily unavailable..." > Appreciate any suggestions > Ken This problem was fairly common when HDDs first went down to 3.5" form factor. The standard solution was to plastic bag them and freeze them. If the head's glued to the disc surface, slamming it's likely to rip the head off. It's a last resort option only. NT |
| "pfjw@aol.com" <pfjw@aol.com>: Jan 24 11:13AM -0800 If the alternative is landfill, many alternate means-and-methods open up. Peter Wieck Melrose Park, PA |
| "Ian Field" <gangprobing.alien1@virginmedia.com>: Jan 24 08:07PM <tabbypurr@gmail.com> wrote in message news:6e1f60bd-8a8c-4afb-bc24-e51f99b2eef5@googlegroups.com... > factor. The standard solution was to plastic bag them and freeze them. > If the head's glued to the disc surface, slamming it's likely to rip the > head off. It's a last resort option only. Ripping stuck stuck heads off wasn't very unusual with old drives that had exposed flywheel on the spindle motor. back in the days of head steppers - you could sometimes get at that too. Never tried putting one in the fridge, but it sounds less likely to do damage - if that doesn't work; resort to violence. Clonking it on the desk might free it - too little wont free it, too much might shift coating off the platters. some drives sense failure to spin up and pulse the head servo to try and free it - careful timing when you clonk it might add that little bit extra that helps the drive fix itself. |
| The Real Bev <bashley101@gmail.com>: Jan 24 12:10PM -0800 Worst case: give them to the children to disassemble for the magnets. You need a REALLY tiny Phillips for the last screws. -- Cheers, Bev If trees could scream, would we be so cavalier about cutting them down? We might, if they screamed all the time, for no good reason. - Jack Handy |
| Pat <pat@nospam.us>: Jan 24 03:20PM -0500 On Wed, 24 Jan 2018 20:07:07 -0000, "Ian Field" >the platters. some drives sense failure to spin up and pulse the head servo >to try and free it - careful timing when you clonk it might add that little >bit extra that helps the drive fix itself. I always tried a mechanical fix BUT NOT slamming them down or hammering on them. Rotate them! If you hold them with your fingers on the sides and rotate them as quickly as you can, the mass of the platters tries to keep them stationary while you rotate the case. I haven't tried that in years since I haven't needed to, but it used to work. |
| Mike_Duffy <mqduffy001@bell.net>: Jan 24 03:58PM -0500 On Wed, 24 Jan 2018 15:20:00 -0500, Pat wrote: > I always tried a mechanical fix BUT NOT slamming them down or > hammering on them. Rotate them! If you hold them with your fingers > on the sides and rotate them as quickly as you can, Agree. If you want to augment the torque by a few orders of magnitude, get a flat sanding attachment for a drill and duct tape the disk to the attachment. You should be able to quite accurately guess the position of the main axis by looking at the housing; if not find the model# on the web and look for a service document with a cutaway view. Presuming your drill is reversable, you can easily alternate the torque between successive trigger pulls if the drill is clamped. The goal is not to spin it fast; rather to quickly cause it to reverse direction. |
| dplatt@coop.radagast.org (Dave Platt): Jan 24 01:40PM -0800 In article <gbqh6dd69pkn29i6icke6r32cg1ij6jlu5@4ax.com>, >platters tries to keep them stationary while you rotate the case. I >haven't tried that in years since I haven't needed to, but it used to >work. +1 to this. It worked well enough for me, years ago, that I was able to do some data rescue from a couple of drives which declined to spin up on their own after sitting idle for a year or two. |
| John Robertson <spam@flippers.com>: Jan 24 03:48PM -0800 On 2018/01/24 1:40 PM, Dave Platt wrote: > +1 to this. It worked well enough for me, years ago, that I was able > to do some data rescue from a couple of drives which declined to spin > up on their own after sitting idle for a year or two. "Shake & Bake" were the methods used to get stuck drives to spin up in the 80s. The shake was a twist as described, the bake was to warm the unit to around 100C to soften the lubes...and then you immediately sucked the data off and trashed the sick drive. John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
| philo <philo@privacy.net>: Jan 24 05:54PM -0600 > When in doubt, get a bigger hammer! > Peter Wieck > Melrose Park, PA Had an MFM drive I got to work by standing on end. If a "jerk" does not do the trick on an ATA drive I've also opened them up and gentry nudged the arm. Back up at once as the drive will not function long |
| Clifford Heath <no.spam@please.net>: Jan 24 10:01PM +1100 On 25/01/18 08:40, Dave Platt wrote: > +1 to this. It worked well enough for me, years ago, that I was able > to do some data rescue from a couple of drives which declined to spin > up on their own after sitting idle for a year or two. Around 1992 we had to do that (after each power failure) on a Fujitsu Eagle hard drive. Pretty difficult; it took two strong people to coordinate a twist on a 60kg drive without dropping it. |
| Jeff Liebermann <jeffl@cruzio.com>: Jan 24 09:46AM -0800 On Tue, 23 Jan 2018 17:44:12 +0000 (UTC), Harold Newton >Theoretical question: >Q: How would T-Mobile *know* if I *moved* the femtocell and/or repeater to >a different location altogether than my own house? You do the grunt work this time. Dig into the instructions for the Femtocell box and see if it has a GPS inside. If it's not clear, grab the FCCID and look it up on the FCCID site. If it has a GPS, T-Mobile will know where you're located. Whether they do anything about a change in location is unknown. I've moved a Verizon femtocell box about 50 miles without any problems. However, that was inside Verizon territory. If you move your T-Mobile femtocell to some location where T-Mobile doesn't claim to have service, I have not idea if they will thank you for improving their footprint, disconnect your service, or something in between. Good luck. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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